Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751527AbcJZEft (ORCPT ); Wed, 26 Oct 2016 00:35:49 -0400 Received: from mail-pf0-f175.google.com ([209.85.192.175]:33821 "EHLO mail-pf0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750960AbcJZEfs (ORCPT ); Wed, 26 Oct 2016 00:35:48 -0400 Date: Wed, 26 Oct 2016 13:43:59 +0900 From: AKASHI Takahiro To: Rusty Russell , Jessica Yu Cc: Kees Cook , "kernel-hardening@lists.openwall.com" , LKML Subject: Re: [kernel-hardening] [PATCH] module: extend 'rodata=off' boot cmdline parameter to module mappings Message-ID: <20161026044358.GY19531@linaro.org> Mail-Followup-To: AKASHI Takahiro , Rusty Russell , Jessica Yu , Kees Cook , "kernel-hardening@lists.openwall.com" , LKML References: <20161020062458.14014-1-takahiro.akashi@linaro.org> <20161021011210.GT19531@linaro.org> <87wpgw3r2r.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87wpgw3r2r.fsf@rustcorp.com.au> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3224 Lines: 93 Rusty, Jessica On Wed, Oct 26, 2016 at 10:43:32AM +1030, Rusty Russell wrote: > AKASHI Takahiro writes: > > On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote: > >> On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro > >> wrote: > >> > The current "rodata=off" parameter disables read-only kernel mappings > >> > under CONFIG_DEBUG_RODATA: > >> > commit d2aa1acad22f ("mm/init: Add 'rodata=off' boot cmdline parameter > >> > to disable read-only kernel mappings") > >> > > >> > This patch is a logical extension to module mappings ie. read-only mappings > >> > at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX > >> > (mainly for debug use). Please note, however, that it only affects RO/RW > >> > permissions, keeping NX set. > > This patch looks good (except the minor issues noted by Kees); please CC > the followup version to Jessica as new module maintainer. I think that the new version (v2)[1] addresses Kees' comments already. [1] http://lkml.iu.edu//hypermail/linux/kernel/1610.2/04163.html Thanks, -Takahiro AKASHI > Thanks! > Rusty. > > >> > > >> > This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory > >> > (always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64. > >> > > >> > Suggested-by: Mark Rutland > >> > Signed-off-by: AKASHI Takahiro > >> > Cc: Rusty Russell > >> > --- > >> > v1: > >> > * remove RFC's "module_ronx=" and merge it with "rodata=" > >> > * always keep NX set if CONFIG_SET_MODULE_RONX > >> > > >> > include/linux/init.h | 3 ++- > >> > init/main.c | 2 +- > >> > kernel/module.c | 21 ++++++++++++++++++--- > >> > 3 files changed, 21 insertions(+), 5 deletions(-) > >> > > >> > diff --git a/include/linux/init.h b/include/linux/init.h > >> > index e30104c..20aa2eb 100644 > >> > --- a/include/linux/init.h > >> > +++ b/include/linux/init.h > >> > @@ -126,7 +126,8 @@ void prepare_namespace(void); > >> > void __init load_default_modules(void); > >> > int __init init_rootfs(void); > >> > > >> > -#ifdef CONFIG_DEBUG_RODATA > >> > +#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX) > >> > +extern bool rodata_enabled; > >> > void mark_rodata_ro(void); > >> > #endif > >> > > >> > diff --git a/init/main.c b/init/main.c > >> > index 2858be7..92db2f3 100644 > >> > --- a/init/main.c > >> > +++ b/init/main.c > >> > @@ -915,7 +915,7 @@ static int try_to_run_init_process(const char *init_filename) > >> > static noinline void __init kernel_init_freeable(void); > >> > > >> > #ifdef CONFIG_DEBUG_RODATA > >> > -static bool rodata_enabled = true; > >> > +bool rodata_enabled = true; > >> > >> Is there a mismatch here between the extern ifdef and the bool ifdef? > >> I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too? > > > > Yes. > > > >> Also, can you mark this as __ro_after_init, since nothing changes it > >> after the kernel command line is parsed? > > > > Yes, yes. > > > > Thanks, > > -Takahiro AKASHI > > > >> Otherwise, this looks fine to me. > >> > >> -Kees > >> > >> > >> -- > >> Kees Cook > >> Nexus Security